A limiting agent of success in the field of drug application, especially in Anesthesiology it is the very means of administering anesthetics. Surveys are conducted in order to discover more effective and less toxic local anesthetic and to improve the equipment used for the application of the drug.
Much of the discomfort generated by the needles is due to its improper handling, however, these instruments have real limitations that make them liable to induce pain.
The mostly used syringe in health care is the aspiration, cartridge type, metal, of breech loading, traditionally called carpule, which, being manual, requires from the professional the condition to introduce the needle with extreme lightness, inject the anesthetic liquid very slowly, but in opposition and simultaneously press the plunger with strength to achieve the penetration of the liquid, especially on certain sites where the tissue is very rigid, such as the subperiosteal region, for instance. The size and cold aspect of the metal associated with the excessive pressure on the syringe plunger, causing very rapid ejection of the anesthetic and/or rapid penetration of the needle end up causing varying degrees of discomfort in individuals.
The state of the art discloses more complex devices for local anesthesia to replace the conventional model. For example, syringes which do not require the use of needle, injecting the anesthetic under high pressure, those that electronically control the release of the anesthetic liquid flow, and plastic syringes, smaller and lighter.
In the 70's a syringe was developed, which was capable to automatically control the anesthetic administration rate, allowing a continuous and regular flow of local anesthetic [HODOSH, M; COMETTA, C.; SHKLAR, G. A new method of injecting local anesthetic painlessly—the Sublimator. Pharmac. Ther. Dent., New York, 2: 65-70, 1975].
In the 80's there came the automatic electronic syringe that in addition to controlling the injection rate also enables the automatic aspiration [MALAMED, S. F. manual of local anesthesia. 3. Ed. Rio de Janeiro, Guanabara Koogan, 1993. 225p].
In Brazil, a similar model, called Control Inject, launched in 1996, performs the electronic control of dosage and drug administration rate, in addition to performing the aspiration, automatically, ensuring continuous and regular flow of the anesthetic solution obtained by the electronic control of the rate and, therefore, the pressure with which the anesthetic is injected into the tissue, providing a more comfortable anesthesia for the patient.
When a fluid is injected into the tissue, there is an increase in the tissue pressure which depends on the speed at which the fluid is injected, the tissue distension capacity and volume of solution injected. An excessive increase in pressure can cause tissue damage resulting in discomfort for the patient during and after the injection. Injections applied with greater volumes and speeds produce higher pressures [ROOD J. P. The pressures created by inferior alveolar injections. Br Dent J 144: 280-282, 1978].
Slow injection of the local anesthetic is one of the means to produce an atraumatic injection. In higher density tissues and with greater adherence to the bone the slow injection is even more important. The rapid injection of the anesthetic solution produces a high tissue pressure that lacerates the soft tissues, causing pain during injection and irritability when the local anesthesic effect ceases [MALAMED, S. F manual de anesthesia local. 3. Ed. Rio de Janeiro. Guanabara Koogan, 1993. 225p]. The slow injection, in contrast, allows the solution to diffuse throughout the normal tissue planes without producing postoperative discomfort [BOMBANA, A. C. Illustrated manual of local anesthesia applied to the dental clinic. 4th ed., Sao Paulo, Laboratório Cristália, 1995, p. 31.].
The initial penetration of the needle should be as minimal as possible, just enough so that the bevel of said needle penetrates the skin/mucous to allow the drug used is deposited in the tissues. Still, the penetration of the rest of the needle must happen slowly and gradually allowing the drug's action.
In this context, there are automatic guns fitted with a retractable needle which protrudes externally to the gun's housing as pressure occurs on the plunger for release of the anesthetic.
Document US2005261634 discloses an injection device comprising an elongated body including a container with medication, means for connecting a needle to the container, triggering means capable of injecting a dose of medication after activation, activating means capable of activating said triggering means, a needle shield placed in the referred to body and that can slide between an extended position and a retracted position relative to said body, said needle shield designed in a way that upon penetration of the needle, and dislocated to its retracted position, acts on said activating means, which, in turn, activates said triggering mean and injects a dose.
Document U.S. Pat. No. 6,099,503 discloses a portion of the needle housing that includes a tube mounted so as to slide axially relative to said member of rearming between a rest position, in which it covers the needle of the syringe and a triggering position in which it acts as a triggering element to release the trigger and activate the injection means.
Document 20090326482, by Mark N. Hochman, of Orangeburg, N.Y., US, discloses a device that administers dental anesthetic into intraligamentary tissues characterized by being provided with electronic system, which calculates the tissue pressure and informs the professional, through sound and bright signals, which will serve as delimiters for the professional to identify the tissue in which he is applying the drug.
In April 2007, quoted inventor wrote an article reviewing standards techniques for intraligamentary injection, also referring to the device patented by him [http://www.ncbi.nlm.nih.gov/pubmed/17487044].
Document BR8802885 of the same author, describes a device for puncture control which allows controlling, safely and effectively, the insertion of a needle into the mucous during puncture, so that it penetrates only in areas previously anesthetized by topical medication by suction of the mucous against the needle bezel, to the extent necessary for the anesthetic liquid to be administered.
Document BR102014012252-4, of the FEDERAL UNIVERSITY OF CEARA, ADJUSTABLE DEVICE FOR NEEDLE INSERTION describes a wrap device of needle of syringes, made up of plug-pieces, which protects and hides said needle controlling the level of needle penetration in the object, with adjustable size, allowing the user to adjust the length of the needle that will be inside the device and the extension that will be exposed.
However, the documents of the state of the art disclose applicators wherein the head of the needle is projected jointly design with the plunger compression, exposing the needle to the application, allowing controlling the plunger movement to control the injection fluid, for example. However, the professional still performs manual control of needle penetration into the tissue.
However, the state of the art does not describe an applicator device which allows programming the force/speed of penetration of the needle to overcome the tissue resistance, so that the applicator manually controls the penetration of the needle. In this applicator, it is performed the automatic control of the movement of the suction chamber, which, therefore, controls the penetration of the needle into the mucous, allowing the regular administration, repeatability and force/speed of programmed injection to overcome the tissue resistance and may be associated with other functions, such as release control of drug/anesthetic flow, mucosal suction, head vibration to massage the mucous, among others.